The use of simulators for the training and assessment of operators of equipment ranging from aircraft to plant equipment allows these tasks to be conducted in a controlled environment where predetermined training or assessment scenarios may be employed to train or determine the competency of an operator. Clearly, the use of simulators as opposed to the actual equipment itself provides a number of benefits. The primary benefit is that the equipment remains free for use. Where an operator is being trained, the use of a simulator also allows the training to be done in an environment where the safety of the person being trained is not put at risk. This also ensures that the equipment is not at risk of being damaged. Another benefit of the use of simulators is that an operator can be trained or assessed on a scenario which in practice would be difficult to replicate in the actual operating equipment.
A simulator system will typically include a physical replica environment that replicates the operating environment of the equipment being simulated. This replica environment will often include a number of operator controls whose outputs are directly monitored by a simulation system processor which implements in real time a simulation model that models the interaction of the piece of equipment with the physical environment and also stimulates the replica environment based on the expected behavior of the equipment as it interacts with the physical environment. This stimulation may range from the simple driving of indicators such gauges and the like to the direct physical manipulation of the replica environment such as in the case of a motion platform which will move the replica environment based on the actions of the operator.
Often a critical component of a simulation system is the visual presentation system which provides a visual display to an operator located in the replica environment. As would be appreciated by those of skill in the art, the operation of most items of equipment relies heavily on the ability of an operator to view, interpret and ultimately act upon visual cues that happen in the physical world. Accordingly, for a simulator to provide an effective training or assessment tool it is necessary to reproduce what would normally be seen by the operator. The more accurate the imitation of what would be seen, the more effective the simulator will be as a training or assessment tool.
Commonly, visual presentation systems include one or more screens upon which are displayed a representation of a three dimensional (3D) world which is regenerated based on the simulated position of the equipment in the 3D world model. As an example, a train simulator which simulates the operation of a train moving on a track will display on screens positioned around the replica environment what would be viewed out of the windows of the driver's cabin (i.e. the replica environment) which is dependent on the calculated position of the driver's cabin on the track. In this manner, a front screen would represent the view of the oncoming track and side screens would represent the view seen to either side of the driver's cabin.
Typically, visual presentation systems involve the projection of an image onto a screen that is placed at a distance beyond the physical window of the replica environment. Projection of the image may be achieved with standard projection systems such as an LCD based projector combined with a suitable projection surface or the use of collimated screen type displays which function to make the image appear in the distance.
Visual presentation systems of this type suffer from a number of significant disadvantages. The main disadvantage is that the degree of simulation of parallax effects (i.e. a respective change in image with head movement) is directly dependent on the distance between the screen and the window and the size of the screen, thereby directly impacting on the size of the simulation system. Because of the size of the screen there is also an associated requirement for a high power projection system to maintain uniform brightness of the image over the projection screen. Another important disadvantage is the inability to simulate windscreen effects with any degree of realism. These include effects such as rain droplets, snow build up, dirt and mud or other windscreen artifacts such as glass tint or aberrations or damage such as cracking or chipping.
In one attempt to address these disadvantages, the image is projected directly onto the window of the replica environment. This reduces the size of the screen and hence that of the simulator and hence addresses the size related issues referred to above and also allows window effects to be simulated. However, because there is no simulation of parallax effects, simulation systems based on visual presentation systems of this type provide a poor simulation of a 3D world due to the “painted on window” effect inherent in projecting the image directly onto the window.
There is therefore a need for a visual presentation system for a simulator capable of improving the representation of a 3D world to an operator of the simulator.